The invention relates generally to an electrical storage battery, and more particularly to an assembly and a method of manufacture for an electrical storage battery expected to find use in conjunction with an implantable medical device, but which may also find use in other applications.
Electrical storage batteries are now in use in a wide range of applications. This range of applications is expected to increase in the future as storage battery technology continues to improve. As improved battery technology allows battery use in more, and more demanding, applications, the requirements imposed on the batteries' physical construction increases as well.
For example, new battery technologies have yielded small and lightweight batteries with long storage lives and high energy output capabilities. This has allowed the use of batteries in new applications such as permanently implantable medical devices including cardiac pacemakers and implantable cardiac defibrillators. Innovators will surely develop other battery-operated medical devices as medical practitioners' understanding of human anatomy and electrophysiology continues to improve.
Batteries for permanently implantable medical devices have very strict requirements. Such batteries should have very long useful lives, thereby allowing long periods between implantation and surgical replacement. The batteries should therefore be capable of high total power output, and have very low self-discharge rates.
Some devices require very high power output rates. For example, an implantable cardiac defibrillator must charge its capacitor and deliver an electrical charge to reestablish the normal rhythm of a beating human heart, preferably within a very few seconds. A battery for such a device must provide a very high energy-output rate to charge the capacitor as quickly as possible.
Batteries intended for permanent implantation in a human patient must be highly reliable over a long time. All internal components must be robust and reliable, and the connections between them stable and secure. Battery failure in an implantable medical device means surgical replacement in the best case. Battery failure at a critical moment can cause the patient's death.
An implantable device must be compatible with the patient's own internal body chemistry. In devices where the body or bodily fluids may contact the battery, the exterior of the battery must be of sufficiently biocompatible materials. The battery must include highly reliable sealing components, moreover, to isolate the components inside the battery and to insure that no battery electrolyte leaks out of the external case that encloses and contains the electrodes.
Some newer batteries include a remote recharging capability. These batteries can be recharged by a charging device disposed a short distance away from the battery. This is of course highly advantageous in an implantable medical device, because the battery can be recharged without invasive surgery to the patient's body.
It is advantageous for any battery, as with any manufactured article, for the manufacture and assembly to be made as simply, reliably, and cheaply, as possible. The battery should include as few parts as are reasonably necessary, and those parts should be easy and quick to assemble.
There is a substantial and increasing need for new batteries, and for related manufacturing methods, that will provide batteries having long lives, high power output rates, and high total energy delivery. The batteries should be reliable and safe for permanent human implantation. Where appropriate, the construction of the battery should lend itself readily to remote recharging according to known and future methods. Finally, it would be advantageous if such batteries were amenable to inexpensive and simple manufacture without unduly compromising either the operating capabilities or the long-term reliability of the battery.
Batteries incorporating the construction of this invention will have these characteristics to greater and lesser extents and in different combinations according to the particular requirements of the uses for which those batteries are designed.